Seatbelt restraint systems for restraining an occupant in a vehicle seat of a motor vehicle play an important role in vehicle crash situations. Seatbelt restraint systems commonly have a lap belt section and a shoulder belt section. In general, the lap belt section and the shoulder belt section are connected together at one end. A seatbelt restraint system includes a latch plate at the connected end. The seatbelt restraint system also includes a buckle device connected at one end by cable, webbing, or the like that is attached directly or indirectly to the vehicle structure. The buckle receives the latch plate to be buckled together. When the buckle and the latch plate are buckle together, the seatbelt restraint system restrains movement of the occupant during a collision.
Various designs for buckle devices including locking and releasing mechanisms for selectively coupling the buckle with the latch plate presently exist. Some non-limiting examples of buckle devices are described in U.S. Patent Application Publication No. 2008/0163468, filed Mar. 13, 2008, U.S. Patent Application Publication No. 2015/0166005, filed Jun. 18, 2015, and WO 2015/128345 claiming priority to DE 10 2014 102 568.7, filed Feb. 27, 2014, which are commonly owned by the assignee of the present application and are hereby incorporated by reference in their entirety for all purposes. Generally, a buckle device includes a main body or buckle housing that receives a latch plate when inserted into the buckle device. Once inserted, a spring urges a latch member to engage the latch plate in a direction in which the latch plate is latched or coupled to the buckle housing. A lock member allows the latch member to maintain the latched condition and a push-button can be actuated to unlock the lock member and release the latch plate from the latched condition.
In such buckle devices, it may be necessary to determine the latch state (e.g., latched or unlatched condition) of the tongue plate with the buckle housing. One conventional approach is to use a switch that is packaged in the buckle device and that is configured to monitor whether the latch plate is coupled or not coupled to the buckle device. This information is transmitted from the buckle device via a switch wire harness and used, for example, for operating an indicator lamp, for controlling a belt winding force via a retractor, or by an airbag electronic control unit (ECU) for determining whether or not to deploy an airbag.
Unfortunately, the buckle switch wire harness can be vulnerable to wire fracture from tension being applied to the switch wire harness, for example, from everyday use, repetitive movements, or the like of the buckle device. Moreover, as buckle designs become more compact, the amount of room available in the buckle device to incorporate adequate strain relief for preventing such wire fractures has become minimal. Accordingly, there is a need to provide a seatbelt buckle apparatus for a motor vehicle that can address one or more of the foregoing concerns.